Signaling system



Oct. 20, 1942. M. w. MUEHTER 2,299,645

SIGNALING SYSTEM Filed June 4, 1940 INVENTOR M. W. MUEHTER BY XXM ATTO R N EY Patented Oct. 20, 1942 UNITED STATES PATENT OFFICE SIGNALING SYSTEM Application June 4, 1940, Serial No. 338,679

19 Claims.

This invention relates generally to signaling systems and more particularly to signaling systems wherein it is desired to initially transmit a simple code, interpret the code and retransmit a different code to any desired point.

This invention finds particular application in fire alarm systems wherein it is advantageous to sound a gong or siren for the purpose of announcing the occurrence of a fire and its particular location. Rather than utilize a number of complicated transmitters together with complicated central station apparatus, it is desired to provide a system adapted to use simple transmitters of the type which send a code of one ortwo digits to a central office. At the central office there is provided a circuit for interpreting the code, retiming the occurrence of code impulses so that a siren may follow the code and retransmitting a different code having a different number of digits to the siren or gong.

It is also necessary in this type of system to provide for non-interference between transmitters as well as successive reception of signals by the central station apparatus whereby confusion of signals is prevented. It is also desirable to arrange the central station apparatus in such a manner that code assignments may be altered to suit the demands of the system whether it be the mere change of a code assigned to one station or change in the number of digits in the code assigned to a particular station. Furthermore, it is necessary to prevent breaks in the transmission line from operating the alarm device to give false alarms.

Accordingly the principal object of this invention is to provide a signaling system wherein fast transmission of code impulses is possible and such code impulses may be converted into a code having a different number of digits which are spaced apart sufiiciently to operate audible signaling device.

A further object of this invention is to provide a system for converting a given code signal into another code signal having a different number of digits and a different time relation between code impulses.

Still another object of this invention to provide a signaling system adapted for transmission of fire alarm signals wherein a given code is converted into a different code which may be repeated through a predetermined number of rounds.

A still further object of thisinvention is to provide a signaling system wherein box codes are converted into difierent codes and. interference between box signals and code signals in the process of retransmission is prevented.

Other objects and advantages of this invention will be apparent from inspection of the specification and accompanying drawing wherein the 2 from a central office to a subscribers premises and includes a number of transmitting boxes I disposed therein in any desired fashion to afford maximum protection depending upon whether the system is used for fire protection or some other form of protective signaling. Each transmitting box I is of a conventional type which includes a set of contacts operated by a cam wheel for successively breaking the loop circuit to thereby transmit a predetermined code of at least one digit. The loop circuit terminates at the central office and controls a box relay. 2 which is normally energized and therefore is'successively deenergized in accordance with the break impulses which form the box code.

The central office equipment includes a siren l8 for sounding an alarm in the form of a code signal. which may comprise a different number of digits from that in the box code. This siren is controlled by a code relay 8 which responds to a switching contact 2 actuated by motor l5 under the control of a coding circuit which will be subsequently described. The loop circuit is continuously energized by alternating current from source iii and a rectifier 3 is provided for rectiiymg the alternating current, which supplies the loop circuit, to supply direct current to the central omce circuits. This rectifier 3 is connected into the alternating current circuit by means of several switching circuits which will the described subsequently.

The box relay 2 initially switches in the rectifier 3 and controls a timing relay 4 which is of the slow-release type and which is actuated in response to the first break impulse of the code signal to switch control circuits and start the operation of a counting selector CS. The counting selector CS is stepped in accordance with and registers the first round of box signals. At the same time the timing relay 4 maintains the connection of the rectifier 3 to the alternating current source IE3 whereby current is supplied to the central oifice switching circuits. After the tim-- ing relay 4 has started the counting selector CS, the switching relay I is energized by the timing relay 4 and the selector CS, and after the first complete round of signals from the box, the timing relay 4 becomes deenergized and the code switch TS becomes energized through contacts controlled by the timing relay 6 and the switching relay I. In the meantime cam operated contacts driven from the shaft of the code selector TS close to maintain power on the rectifier unit 3 and another set of similar contacts interrupt power to the counting selector CS whereby it ceases to operate and registers the code transmitted from the alarm box I.

The counting selector CS comprises three banks of contacts as illustrated in the drawing, each bank simultaneously registering the code transmitted from the alarm box. The code selector TS also includes three banks of contacts, each bank containing fifty contacts. One bank of this code selector TS is connected to the counting selector CS in such a manner that the box code registered on the counting selector CS is converted to a three-digit code as will be described in a subsequent description of the operating circuits. The code selector TS is driven through a series of steps and therefore requires an impulse device as a source of power. This impulse device comprises the motor I5, and a contact I driven thereby which closes a circuit for energizing the code selector TS, and the contact 2 for controlling the siren control relay 8. The motor I is started by the code selector TS since one bank thereof establishes a power circuit to energize the motor. The code selector TS steps from one contact to another under control of motor I5 until a circuit is established through the first bank of counting selector CS to shunt the switching relay I whereby it is released and disables the code relay 8 that controls the siren. Since the code relay 8 has been energized at each step of the code selector TS, one digit of the code will have been sounded on the siren. Release of the switching relay I closes a self-stepping circuit for the code selector TS whereby this selector self-steps until its selfstepping circuit is opened at an idle contact thereon. The motor I5 then recovers control of the selector TS and the switching relay I is again operated whereby selector TS again steps until a second shunt circuit is created through bank 2 of selector CS so that the successive digits are transmitted in accordance with the operation of the selectors CS and TS.

The circuit illustrated in the drawing provides facilities for transmitting a code of three digits and after one complete round of the code is transmitted, the switching relay I causes repetition of the code until four rounds have been completed,-at which time a cam contact 3 on the shaft of the code selector TS interrupts the power supply of the rectifier 3 whereby the complete central office circuit is restored to its normal condition.

' If the second box operates during the time that the retransmission of the first signal is occurring a timing relay prevents interference with retransmission. The timing relay also prevents falseoperation when a break occurs in the line. The circuit will now be described in detail with reference to the drawing. The box loop may include up to 22 boxes such as shown at I, each box including a code wheel having a single digit consisting of three to 24 consecutive teeth out thereon. Code numbers I and 2 are not used as similar signals due to breaks in the circuit or tests are apt to cause false alarms. Signals are transmitted when the teeth on the code wheels interrupt the loop circuit.

Starting operation.-In response to the break caused by the operation of the fire alarm box code Wheel springs, the normally energized code relay 2 will operate, and follow the code as determined by the breaks transmitted. On the first release of relay 2, its break contact 3 applies alternating voltage from source II] to the input side of the rectifier 3 which in turn applies rectified voltage to the local control circuits. Timing relay 4, a slow release relay, is energized at this time from plus battery through contact l of relay 2 through relay 4 to minus. Closure of the contact I of relay 4 applies a further locking circuit to the A. C. source If] at the input of the rectifier 3. The relay 4, as previously mentioned, is of the slow release type and does not respond to the space between impulses, that is, it does not drop out when relay 2 is energized between break impulses whereby circuits controlled by its contacts do not respond to break impulses.

Counting seZect0r.-When make contact 5 of relay 2 closes after each break impulse, the counting selector CS is energized and makes a number of steps in response to the code transmitted through the circuit traced from plus through position EU on transmitting selector bank TSS, through make contact 5 of relay 2, make contact 3 of relay 4, cam contact I of selector TS closed at steps 49 and 50 of switch TS, and the stepping coil CSS to minus.

At position 2 of CS, selecting or switching relay 1 operates through the circuit traced from minus through resistance 6, make contact 5 of relay 4, selector bank CSI, position 2, through coil 2 of relay I to plus. A locking circuit for relay I is completed by the closure of its contact I.

At the end of the first round of signals transmitted from the fire alarm box the selector CS will have advanced to a position as determined by the code which corresponds to the number of the box, and during the space after the first round of signals, the relay 4 will drop out and energize TS which advances to position 1 in selfinterrupted drive. This circuit may be traced from plus through bank TSI position 50, through make contact 3 of relay 1, break contact 2 of relay 3, cam operated back contact 2 of selector TS, interrupter contact of selector stepping coil of TSS, and stepping coil TSS to minus. The interrupter contacts of TSS break the stepping circuit for the selector TS and allow it to ad-- Vance to position 1. The cams geared on selector TS operate several sets of contact springs. Contact springs 3 of selector TS, I of relay 6, and contact 3 of relay 2 maintain power on the rectifier 3. Contact springs I of selector TS in terrupt power to coil CSS of selector CS to prevent its operation during subsequent rounds of signals from the fire alarm box I prior to completion of the siren code transmission. Back contact 2 operated by the cam of selector TS opens the above traced operating circuits of selector TS.

Impulse cZevice.At position 1 of transmitting selector TS a circuit is closed from power source I ii through selector bank TSZ, position 1, through the telechron motor I5. This motor drives a contact device I6 that provides impulses for stepping the TS selector and for energizing the siren control relay 8. On the first closure of the impulse contact I of device I 6 the TS selector is energized through the circuit traced from plus, through make contact 5 of relay 1, make contact I of device I6, and stepping coil TSS to minus. At the same time the coding relay 8 operates through the circuit traced from one side of the source, through the coil of relay 8, make contact 6 of relay I, impulse contact 2 of device I6, position 1 on bank TS2 to the other side of the source Ill. The operation of the contact on the coding relay 3 applies local battery to the siren I8 for the sounding of the signal. The first break of contact I of device I6 deenergizes the selector stepping coil TSS, allowing selector TS to advance to position 2.

Coding operation-Let us assume that a code 4'63 is to be retransmitted on receiptof a signal from a fire alarm box with a code wheel cut with '7 teeth. From the previous description it will be recalled that the CS selector will be at position '7' for this code. Position 7 on selector banks CSI, CS2, and CS3 will be connected to positions 5, 18 and 26 respectively on bank TS3. The TS selector will advance in response to the operation of contact I of device I5 through the circuit previously traced until position 5 is reached, four impulses at the same time having been transmitted through the contact of relay 8 to the siren I8. The operation of relay 8 has previously been traced.

At position 5 the relay winding 2 of relay I is shunted by the circuit traced from plus through bank TS3 position 5, and through bank CSi position 7, the relay '1 therefore releasing.

With the release of relay 7, a self-stepping circuit for selector TS is set up which may be traced from plus through bank TSI position 5, break contact 4 of relay I, interrupter contact of TSS and coil TSS to minus. The selector continues self-stepping through positions 6 to 1 until it reaches position 11 at which time this circuit is open. At position 11 a slow step is made to 12 through TSI position 11, impulse contact I of device I and coil TSS to minus. This provides for the necessary space between digits of the code.

At position 12, relay i again operates this time through its winding I, through the circuit traced from plus through bank TS3 position 12, winding I of relay I to minus. The locking circuit through winding 2 of relay 1 again is established. In a similar manner to that described for the first digit, six slow impulses are transmitted to the coding relay 8 and the selector TS advances to position 18 at which point relay 1 is again shunted out. Again a self-stepping circuit is set up for TS which advances to position 21 and then in a slow step to 27.

The third digit is transmitted in a similar manner to that previously described.

After the first round of the code is transmitted, the selector TS self-steps, through a circuit on bank TSI positions 34 to 46, contact 4 of relay 7, interrupter contact of coil TSS and coil TSS to minus, to position 47, from which point it makes slow steps to position 49 through the contact I of device I6, and positions 47 and 48 on TSI. At positions 49 and 50 of TSI selfstepping circuits are set up which may be traced from plus through bank TSI, positions 49 and 50, through cam operated make contacts 4 of selector TS, interrupter contact of coil TS5, and stepping coil TSS to minus. The selector TS buzzes to position 1 at which point the relay '1 is energized through the circuit traced through bank TS3 position 1, and the winding I of relay I to minus. The retransmission continues as before through the second, third and fourth rounds of signals to position 49 as before. At this position the geared cam contacts of selector TS restore to the normal position. The counting selector CS then advances through a selfstepping circuit to position 50, this circuit being traced from plus through TS3 position 49, camoperated off-normal contact I, interrupter contact of coil CSS, cam contact I of selector TS and stepping coil CSS to minus. At position 50 the cam-operated off normal contact I of selector CS breaks its circuit leaving the selector CS in its normal home position and at the same time closes the back contact to energize a selfstepping circuit to the TS selector, which may be traced from plus battery through TS3 position 49, cam-operated contact 2 of selector CS, break contact 2 of relay 4, cam contact 2 of selector TS, interrupter contact of coil TSS, and stepping coil TSS to minus. The selector TS advances to position 50.

At position 49 only the contact on bank TSZ is maintaining the A. C. supply on the input side of the rectifier I i], the other contacts having previously opened during some point of the operation. When the selector TS advances to position 50 this A. C. supply is interrupted and all local power is removed on the D. C. side of the rectifier.

Second box in operation Let it be assumed that a second box has been operated on the line circuit during the time that the retransmission from the first box is being completed by the control unit. It this case the relay 2 is responding to the signal so therefore relay 4 will be energized.

At the end of the fourth round of transmission from the siren control, if relay 4 is energized due to the second box in operation, selector TS does not return to normal until relay 4 releases as the contact 2 of relay 4 in the restoring circuit is opened at this time. When relay 4 releases between the rounds of the new signal, selector TS returns to normal through the circuit previously traced and all equipment clears out in readiness for setting up a new code.

N 0 top features Should one or two impulses be transmitted over the line circuit due to a break or testing, selector CS will advance as for a code transmission. After one impulse when relay 4 releases, selector CS returns to its home position through the circuit traced from plus through TS3 position 50, make contact 5 of relay 2, break contact 4 of relay 4, break contact 2 of relay I, interrupter contact of coil CSS, cam contact I of selector TS and stepping coil CSS to minus. Selector CS comes to a stop in the home position 50, as oif-normal contact 3 of CS opens and opens the power connection to the rectifier.

Should two breaks occur in quick succession, relay 4 operates on the first break and on the first reenergization of relay 2, selector CS moves to position 1. On the second break the relay 2 releases and on subsequent reenergization energizes the selector stepping coil CSS but does not allow it to advance to position 2 at this time as relay 2 remains energized. Shortly after, the relay 4 will release and the selector CS will return to its home position through the circuit traced above. Relay 1 does not operate at po-- sition 2 due to the open circuit at contact 5 of relay 4.

Siren code assignments As previously mentioned, the various positions on banks 05!, CS2, and CS3 corresponding to the box code are connected to bank TSS for the siren code desired. For example, a station such as I having eight teeth on the code wheel would step OS to contact 8 of each bank so that conductors may be connected to arbitrarily chosen contacts on T83 to cause transmission of the desired siren code.

The illustrated circuit covers the arrangement for a three-digit code. Should two digit or single digit codes be required, they may be obtained as outlined below.

Two digit codes'.-Points 24 to 33 on T83 are left unconnected. On TS3 point 23' shall be disconnected from coil I of relay 1 and be connected to contact 4 of relay 1 with common strapping of contacts 2|9, I32l, 24-32 and 34-46 of TSI.

Single digit codes-Points It! to 33 on 'IS3 are left unconnected. On TS3 points [2 and 23 shall be disconnected from coil I of relay 7 and be connected to contact 4 of relay 1 with common strapping of contacts 2|G, |3--2I, 2i32 and 3445 of-TSI.

Operation of single and two digit codes.The operation is as previously described except after the completion of the particular code self-stepping circuits are set up which return the selector to position 49 except for positions 22 and 33 when the selector is advanced slowly by the operation of contact I of device #6.

From the above description it is evident that this system is particularly adapted to convert single train impulse codes to codes of more than one digit which may be utilized for operation of any form of indicating or signaling device. It is further evident that the system is flexible in that codes transmitted from transmitting stations may be converted to any desired plural digit code without the necessity of substantial changes within the central oiiice wiring system. Furthermore, the system is so designed that breaks in a line circuit do not cause retransmission of false signals. It has also been provided that regardless of the spacing between received signals the retransmitted signals are sufiiciently spaced to satisfactorily operate audible signaling devices such as gongs or sirens. The system has also been designed to perform its functions in a positive and economical manner and with the simplest form of apparatus and circuits obtainable.

It is not desired that this invention shall be limited to use in any particular form of alarm system as it is evident that any form of alarm signal may be retransmitted to any form of signaling device or receiving station. The particular elements of the system such as the impulse generating device i5 and IS and the various switching circuits may be modified in various ways which will be obvious to those skilled in the ing relay controlled by said transmitter for repeating the code, and a code translating circuit comprising a switching contact controlled by the receiving relay, a counting selector energized by said switching contact in accordance with the code for registering the same, a siren for sounding the code, a transmitting selector for controlling the siren and connections between the selectors for changing the transmitted code to another code having a difierent number of digits.

2. In a signaling system, a transmission line includinga transmitter therein for transmitting a predetermined code signal, a multi-bank stepping switch for registering said code signal and a retransmitting means comprising a selector device connected to said switch and controlled thereby for changing the characteristics of the transmitted code signal in accordance with the number of banks in said switch.

3. In a signaling system, a box loop including an impulse transmitter and a normally energized box relay for repeating the box code in accordance with break impulses, a counting selector for registering the box code, a timing relay energized by said box relay for preparing a circuit to the counting selector and holding the circuit in operative condition throughout the box code period, a switching contact in the counting selector circuit responsive to the box relay for energizing the selector to register the box code, a transmitting selector having a number of banks, one bank having a number of preselected threedigit codes set up thereon, a selecting relay energized by the counting selector and the timing relay and released when shunted by the counting selector and the transmitting selector after a digit has been transmitted, a motor energized by another bank of said transmitting selector for driving said transmitting selector until the selecting relay is shunted and breaks the driving circuit, contacts operated by the selecting relay and another bank of said transmitting selector for closing a self-stepping circuit whereby the switch steps to the starting point of the second digit, contacts closed by the first bank of the transmitting selector for again energizing the selecting relay whereby transmission of another digit is started under the control of the driving motor, a siren and contacts operated by the motor and the selecting relay for energizing the siren in accordance with the code.

4. In a signaling system, a central ofiice including a counting selector for registering a code signal, a transmitting selector having a number of banks, one bank having a number of preselected codes set up thereon, a selecting relay energized by the counting selector and released when shunted by it, a motor energized by another bank of said transmitting selector for driving the same until the selecting relay is shunted and breaks the driving circuit, contacts operated by the selecting relay and another bank of said transmitting selector for closing a self-stepping circuit whereby the switch steps to the starting point of the second digit, contacts closed by the first bank of the transmitting selector for again energizing the selecting relay whereby transmission of another digit is started under the control of the driving motor, a siren and contacts operated by the motor and the selecting relay for energizing the siren in accordance with the code.

5. In a signaling system, a transmission line including a plurality of transmitters therein, a normally energized signal receiving relay c0n nected to said line, a source of alternating current connected to energize the line and the receiving relay, and a code translating circuit comprising a source of direct current, switching contacts closed by said receiving relay, a counting selector connected to and energized by said direct current source in accordance with the actuation of said switching contacts, a transmitting selector controlled by the counting selector for translating the original code and a siren energized by the transmitting selector in accord ance with the new code.

6. In a signaling system, a counting selector having at least three banks of contacts each of which registers the same single train impulse code, means for registering a code thereon, a transmitting selector comprising three banks of contacts, the first bank of which is divided in three sections to provide three code digits, a motor and a contact operated thereby for energizing the transmitting selector, a selecting relay energized by the counting selector for starting the transmitting selector, a coding relay operated by the motor and the selecting relay for repeating code impulses at spaced time intervals, connections from each section of the transmitting selector to predetermined contacts of the counting selector for establishing a shunt circuit at the end of each digit as counted by the transmitting selector for deenergizing the selecting relay to thereby disable the coding relay, a contact operating in conjunction with a second bank of the transmitting selector for completing a selfstepping circuit for said. selector whereby the transmitting selector continues to step and breaks the shunt circuit around the selecting relay for reenergizing the same, contacts on the same bank of the transmitting selector for reestablishing a motor operated circuit for again energizing the transmitting selector to count a second digit of the code.

7. In a signaling system, a counting selector having at least three banks of contacts each of which registers the same single train impulse code, means for registering a code thereon, a transmitting selector comprising three banks of contacts, the first bank of which is divided in three sections to provide three code digits, an impulse generator operated thereby for energizing the transmitting selector, a switching relay energizid by the counting selector for starting the transmitting selector and the coding relay operated by the motor for repeating code impulses at spaced time intervals, connections from each section of the first bank of the transmitting selector to predetermined contacts of the counting selector effected at the end of each digit as counted by the transmitting selector for deenergizing the selecting relay, means operating in conjunction with a second bank of the transmitting selector for completing a elf-stepping circuit for said selector whereby the transmitting selector continues to step and said connections are changed for reenergizing the selecting relay and contacts on the same bank of the transmit ting selector for reestablishing a motor operated circuit for again energizing the transmitting selector to count a second digit of the code.

8. In a signaling system, a multi-bank count-- ing selector for registering a single train impulse code, means for transmitting the code to said selector, a transmitting selector comprising at least tWo banks of contacts, the first bank of which is divided in three sections, each of which is connected to a bank of said counting selector to provide three code digits, a selecting relay energized by said counting selector, a contact operated by said relay for starting the transmitting selector, motor driven means for continuing the operation of said selector, connections from each section of said first bank of the transmitting selector to the counting selector for shunting the selecting relay after each code digit is transmitted and contacts operated by the selecting relay and another bank of said transmitting selector for operating this selector in self-stepping fashion between transmission periods.

9. In a signaling system, a counting selector for registering a train impulse code, means for transmitting the code to said selector, a transmittingselector comprising at least two banks of contacts, the first bank of which efiects transmi" ion of three code digits, a switching relay one gized by said counting selector for starting the transmitting selector, impulse generating means for continuing the operation of said selector, connections from each section of the transmitting selector to the counting selector for shunting the selecting relay after each code digit is transmitted, and contacts operated by the switching relay and another bank of said transmitting selector for operating this selector in self-stepping fashion betwen transmission 'periods.

10. In a signaling system, a counting selector having a number of banks of contacts thereon for registering a code, a transmitting selector comprising at least two banks of contacts for transmitting a code having a diiierent number of digits from that registered on the counting selector, means for operating said transmitting selector at slow speed While the code is being transmitted and means for increasing the speed of the transmitting selector between digit transmissions.

11. In a signaling system, means for registering a single train impulse code, a transmitting means controlled by the registering means for transmitting a code having a different number of digits from that registered on the registering means, means for operating said transmitting means at slow speed While the code is being transmitted and means for increasing the speed of the transmitting selector between digit transmissions.

12. In a signaling system, a counting selector for registering a single train impulse code, a transmitting selector for transmitting a three digit code as predetermined by the code registered on the counting selector, a selecting relay energized by the counting selector for controlling transmission of code impulses by the transmitting selector, circuits established by the count ing selector and transmitting selector for deenergizing the selecting relay upon the completion of transmission of each code digit and contacts operated by the selecting relay and the transmitting selector for completing energizing circuits for driving the transmitting selector through a predetermined number of complete cycles of operation.

13. In a signaling system, a means for registering a single train impulse code, a means for transmitting a three digit code as predetermined by the code registered on the registering means, a switching means controlled by the registering means for controlling transmission of code impulses by the transmitting means, circuits established by the registering means and transmitting means for disabling the switching means upon the completion of transmission of each code digit and means operated by the switching means and the transmitting means for driving the transmitting means through a predetermined number of complete cycles of operation.

14. In a signaling system, a counting selector for registering a single train impulse code, a transmitting selector for transmitting a three digit code as predetermined by the code registered on the counting selector, a selecting relay energized by the counting selector for controlling transmission of code impulses by the transmitting selector, circuits established by the counting selector and transmitting selector for deenergizing the selecting relay upon the completion of transmission of each code digit and contacts operated by the selecting relay and the transmitting selector for completing energizing circuits for driving the transmitting selector through a predetermined number of complete cycles of operation, and a cam operated by the transmitting selector for opening the energized circuit of said selector after a predetermined number of cycles of operation whereby the transmission of code impulses is stopped.

15. In a signaling system, a means for registering a single train impulse code, a transmitting means for transmitting a three digit code as predetermined by the code registered on the registering means, a switching means controlled by the registering means for controlling transmission of code impulses by the transmitting means, circuits established by the registering means and transmitting means for disabling the switching means upon the completion of transmission of each code digit and means operated by the switching means and the transmitting means for driving the transmitting means through a predetermined number of complete cycles of operation and means operated by the transmitting means for opening the energizing circuit of said transmitting means after a predetermined number of cycles of operation whereby the transmission of code impulses is stopped.

16. In a signaling system, a box loop including a plurality of transmitting stations, a box relay connected in said loop for repeating impulses transmitted by said stations, a timing relay energized by said box relay for controlling the central station in accordance with the operation of the box code, a rectifier for energizing the central station apparatus, a contact operated by the box relay for connecting the rectifier to its source of energy and a contact operated by the timing relay for maintaining a voltage across the rectifier during transmission of code impulses.

17. In a signaling system, a box loop including a source of current, a box relay connected in said loop for repeating impulses transmitted within the loop, means energized by said box relay for controlling the central station in accordance with the operation of the box code, a rectifier for energizing the central station apparatus, means operated by the box relay for initially connecting the rectifier to its source of energy and means operated by the central station control means for maintaining a voltage across the rectifier during transmission of code impulses.

18. In asignaling system, a box loop including a plurality of transmitting stations, a box relay connected in said loop for repeating code impulses, a rectifier connected across the box loop for converting A. C. energy to D. C. energy and supplying the central station potential, a slow to release timing relay energized by the box relay to connect the rectifier to the A. C. source, a contact operated by the timing relay for maintaining connection of the rectifier to the source, a counting selector for registering the box code under the control of the timing relay and the box relay, a transmitting selector controlled by the counting selector and contacts operated by the transmitting selector for disconnecting the counting selector from the source of potential after one complete box code has been received whereby interference between successively operated boxes is prevented.

19. In a signaling system, a box loop including a source of current and at least one transmitting station, a box relay connected in said loop for repeating code impulses, a timing relay energized by the box relay, a counting selector for registering the box code under the control of the timing relay and the box relay, a transmitting selector controlled by the counting selector and contacts operated by the transmitting selector for disconnecting the counting selector from the source of potential after one complete box code has been received whereby interference between successively operated boxes is prevented.

MANFRED W. MUEI-ITER. 

